Sheet transitioning in spiral formed structures

ABSTRACT

Spiral forming devices, systems, and methods can be used to join edges of a of a stock material, in a curved configuration, along one or more joints to form tubular structures, such as conical and/or cylindrical structures (e.g., frusto-conical structures). A planar form of the stock material can be formed from a plurality planar sheets coupled to one another in an abutting relationship. By controlling relative orientation and shapes of the plurality of planar sheets forming the stock material and/or by controlling a position of a roll bender used to curve the planar form of the stock material into the curved configuration, the curved configuration of the stock material can be controlled through transitions between sheets to facilitate rolling the sheets to a desired diameter with a reduced likelihood of dimples or other errors and to facilitate fit up between adjacent sheets in the curved configuration.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/183,231 (now U.S. Pat. No. 10,486,212), filed on Nov. 7, 2018, whichis a continuation of U.S. patent application Ser. No. 15/692,461 (nowU.S. Pat. No. 10,201,841), filed on Aug. 31, 2017, which claims thebenefit of priority of U.S. Provisional Patent Application No.62/381,749, filed on Aug. 31, 2016, with the entire contents of each ofthese applications hereby incorporated herein by reference.

GOVERNMENT LICENSE RIGHTS

This invention was made with government support under NSF Phase II SBIRgrant NSF IIP-1353507, awarded by the National Science Foundation. TheUnited States government has certain rights in this invention.

BACKGROUND

In a spiral forming manufacturing process, a sheet of steel is fed intoa mill and continuously roll-formed into a desired shape. For example,using this technique a cylinder or a conical shape can be formed byfeeding sheets of suitably shaped material into the mill andcontinuously joining the curved, roll-formed material along a spiraledge as the material exits the mill. While a variety of usefulstructures such as steel towers for wind turbines can be fabricatedusing this technique, transitions between the sheets used to form thesestructures present certain challenges with respect to meetingmanufacturing tolerances and efficient use of material in the finalstructures.

SUMMARY

Spiral forming devices, systems, and methods can be used to join edgesof a stock material, in a curved configuration, along one or more jointsto form tubular structures, such as conical and/or cylindricalstructures (e.g., frusto-conical structures). A planar form of the stockmaterial can be formed from a plurality planar sheets coupled to oneanother in an abutting relationship. By controlling relative orientationand shapes of the plurality of planar sheets forming the stock materialand/or by controlling a position of a roll bender used to curve theplanar form of the stock material into the curved configuration, thecurved configuration of the stock material can be controlled throughtransitions between sheets to facilitate rolling the sheets to a desireddiameter with a reduced likelihood of dimples or other errors and tofacilitate fit up between adjacent sheets in the curved configuration toincrease the likelihood of meeting manufacturing tolerances in the finalstructure.

According to one aspect, a collection of a plurality of planar sheetscan be collectively dimensioned to form, in a curved configuration, atubular structure, and the plurality of planar sheets can include afirst planar sheet having a pair of first longitudinal edges, a matingedge, and an alignment edge, the mating edge and the alignment edgetogether defining a nonlinear path extending between the firstlongitudinal edges, and a second planar sheet having a pair of secondlongitudinal edges and a lateral edge, the lateral edge extendingbetween the second longitudinal edges, wherein the first planar sheetand the second planar sheet are dimensioned to be positionable relativeto one another in an abutting relationship in which the mating edge ofthe of the first planar sheet complements the lateral edge between thesecond longitudinal edges of the second planar sheet and the alignmentedge of the of the first planar sheet is collinear with one of thesecond longitudinal edges of the second planar sheet.

In certain implementations, in the abutting relationship between thefirst planar sheet and the second planar sheet, the first planar sheetand the second planar sheet can form a continuous surface.

In some implementations, in the abutting relationship between the firstplanar sheet and the second planar sheet, one of the first longitudinaledges of the first planar sheet can be oblique relative to one of thesecond longitudinal edges of the second planar sheet.

In certain implementations, in the abutting relationship between thefirst planar sheet and the second planar sheet, one of the firstlongitudinal edges of the first planar sheet can contact one of thesecond longitudinal edges of the second planar sheet to define asubstantially continuous edge.

In some implementations, the first planar sheet can have a firstthickness, and the second planar sheet have a second thickness equal tothe first thickness.

In certain implementations, the first planar sheet and the second planarsheet can each have an elongate shape, and the first planar sheet andthe second planar sheet can have different lengths.

In some implementations, the pair of first longitudinal edges can beparallel to one another. Additionally, or alternatively, the pair ofsecond longitudinal edges can be parallel to one another. In certaininstances, the pair of first longitudinal edges of the first planarsheet can define a first width, and the pair of second longitudinaledges of the second planar sheet can define a second width equal to thefirst width.

In certain implementations, the mating edge of the first planar sheetcan include at least one linear segment.

In some implementations, the lateral edge of the second planar sheet candefine a linear path between the pair of second longitudinal edges ofthe second planar sheet.

In certain implementations, the lateral edge of the second planar sheetcan define a nonlinear path between the pair of second longitudinaledges of the second planar sheet. For example, the nonlinear pathdefined by the lateral edge can have one or more straight segmentsangled relative to one another. Additionally, or alternatively, thenonlinear path, along which the lateral edge of the second planar sheetextends, can define a chevron. Further, or instead, the nonlinear path,along which the lateral edge of the second planar sheet extends,includes a curvilinear shape.

In some implementations, the first planar sheet and the second planarsheet can each be formed of metal.

In certain implementations, the plurality of planar sheets can becollectively dimensioned to form, in a curved configuration, afrusto-conical structure without in-plane deformation of the planarsheets.

According to another aspect, a frusto-conical structure can include afirst curved sheet having a pair of first longitudinal edges, a matingedge and an alignment edge, the mating edge and the alignment edgetogether defining a nonlinear path extending between the firstlongitudinal edges, and a second curved sheet having a pair of secondlongitudinal edges and a lateral edge, the lateral edge extendingbetween the second longitudinal edges, the lateral edge of the secondcurved sheet and the mating edge of the first curved sheet coupled toone another to form a lateral seam extending from one of the secondlongitudinal edges to another one of the second longitudinal edges, thealignment edge of the first curved sheet forming at least a portion of afirst spiral seam with one of the second longitudinal edges of thesecond curved sheet.

In some implementations, one of the first longitudinal edges of thefirst curved sheet and one of the second longitudinal edges of thesecond curved sheet can be joined along the first spiral seam.Additionally, or alternatively, the first curved sheet and the secondcurved sheet can be coupled to one another at an intersection of thelateral seam, the first spiral seam, and a second spiral seam, and thelateral seam, the first spiral seam and the second spiral seam can beoblique relative to one another at the intersection.

In certain implementations, the first curved sheet and the second curvedsheet can each be formed of metal, and the lateral seam can include aweld coupling the first curved sheet and the second curved sheet to oneanother.

In some implementations, the first curved sheet and the second curvedsheet can be coupled to one another without in-plane deformation.

According to still another aspect, a method can include obtaining aplurality of planar sheets comprising a first planar sheet having a pairof first longitudinal edges, a mating edge, and an alignment edge, themating edge and the alignment edge defining a nonlinear path extendingbetween the first longitudinal edges, and a second planar sheet having alateral edge and a pair of second longitudinal edges, the lateral edgeextending between the second longitudinal edges, positioning the firstplanar sheet and the second planar sheet relative to one another in anabutting relationship in which the mating edge the first planar sheetcomplements the lateral edge of the second planar sheet between thesecond longitudinal edges and the alignment edge of the first planarsheet is collinear with one of the second longitudinal edges of thesecond planar sheet, coupling the mating edge of the first planar sheetto the lateral edge of the second planar sheet along a lateral seam toform a stock material in planar form, curving the stock material into acurved configuration, and spiral welding the stock material to form afrusto-conical structure.

In certain implementations, the lateral seam includes at least onenon-linear segment.

In some implementations, the lateral seam can include at least onelinear segment.

In certain implementations, the first planar sheet and the second planarsheet can each be elongate, and the first planar sheet and the secondplanar sheet can each have different lengths.

In some implementations, spiral welding the stock material to form thefrusto-conical structure includes coupling one of the first longitudinaledges of the first planar sheet, in a curved configuration, to one ofthe second longitudinal edges of the second planar sheet, in a curvedconfiguration.

According to still another aspect, a method can include moving a firstplanar sheet and a second planar sheet in a feed direction through rollbanks of a roll bender, the first planar sheet and the second planarsheet coupled to one another in an abutting relationship, a length ofthe abutting relationship between the first planar sheet and the secondplanar sheet along the feed direction defining a transition length,within the transition length, curving the first planar sheet and thesecond planar sheet with the roll banks of the roll bender set at afirst position, the first planar sheet and the second planar sheethaving different curvature responses to the roll banks of the rollbender set at the first position, and within the transition length,curving the first planar sheet and the second planar sheet with the rollbanks of the roll bender set at a second position different from thefirst position, the first planar sheet and the second planar sheethaving different curvature responses to the roll banks of the rollbender set at the second position.

In certain implementations, the first planar sheet has a thicknessgreater than a thickness of the second planar sheet, and the firstplanar sheet and the second planar sheet can be curved by the roll banksof the roll bender set to the second position when more than half of thetransition length has moved past a center roll of the roll bender.

In some implementations, the first planar sheet can have a thicknessless than a thickness of the second planar sheet, and the first planarsheet and the second planar sheet can be curved by the roll banks of theroll bender set to the second position when less than half of thetransition length has moved past a center roll of the roll bender.

In certain implementations, curving the first planar sheet and thesecond planar sheet with the roll banks of the roll bender set at thesecond position includes moving one or more of the roll banks of theroll bender relative to one another from the first set position to thesecond set position.

In some implementations, the method can further include, along a lengthin the feed direction within the transition length, curving the secondplanar sheet with the roll banks of the roll bender set at a third setposition different from the second set position. For example, arespective curvature response of the second planar sheet to the rollbanks of the roll bender set to the third position is substantiallyequal to a respective curvature response of the first planar sheet tothe roll banks of the roll bender set to the first position such that atleast a portion of the first planar sheet and a portion of the secondplanar sheet are rolled at substantially the same diameter.

In certain implementations, the roll banks of the roll bender can bearranged as a triple roll.

In some implementations, a thickness of the first planar sheet can bedifferent from a thickness of the second planar sheet.

In certain implementations, the thickness of the first planar sheet canbe greater than the thickness of the second planar sheet.

In some implementations, the thickness of the first planar sheet can beless than the thickness of the second planar sheet.

In certain implementations, the abutting relationship between the firstplanar sheet and the second planar sheet includes abutment along one ormore edges that are oblique to the feed direction as the first planarsheet and the second planar sheet moving through the roll bender alongthe transition length.

In some implementations, the abutting relationship between the firstplanar sheet and the second planar sheet can include a curvilinearshape.

In certain implementations, an in-feed angle of the first planar sheetand the second planar sheet along the transition length can be obliqueto an axis defined by one of the roll banks of the roll bender.

In some implementations, the first planar sheet and the second planarsheet can have the same maximum width in a direction perpendicular torespective longitudinal edges of the first planar sheet and the secondplanar sheet.

Other aspects, features, and advantages will be apparent from thedescription and drawings, and from the claims.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic of a wind turbine assembly including a taperedtower.

FIG. 2 is a perspective, exploded view of the tapered tower of FIG. 1including conical segments.

FIG. 3 is a perspective side view of one of the conical segments of thetapered tower of FIG. 1.

FIG. 4 is a top view of a collection of a plurality of planar sheets forforming a portion of the conical segment of FIG. 3.

FIG. 5 is a top view of planar form of a stock material formed from thecollection of the plurality of planar sheets of FIG. 4.

FIG. 6 is a block diagram of a fabrication system.

FIG. 7 is a schematic representation of a spiral forming process carriedout by the fabrication system of FIG. 6.

FIG. 8 is a flowchart of an exemplary method of forming a tubularstructure.

FIG. 9 is a top view of a collection of a plurality of planar sheets.

FIG. 10 is a schematic representation of a curving operation of thespiral forming process shown in FIG. 7.

FIG. 11 is a flowchart of an exemplary method of applying curvature to atransition of planar sheets.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

The embodiments will now be described more fully hereinafter withreference to the accompanying figures, in which preferred embodimentsare shown. The foregoing may, however, be embodied in many differentforms and should not be construed as limited to the illustratedembodiments set forth herein.

All documents mentioned herein are hereby incorporated by reference intheir entirety. References to items in the singular should be understoodto include items in the plural, and vice versa, unless explicitly statedotherwise or clear from the context. Grammatical conjunctions areintended to express any and all disjunctive and conjunctive combinationsof conjoined clauses, sentences, words, and the like, unless otherwisestated or clear from the context. Thus, the term “or” should generallybe understood to mean “and/or” and so forth.

Recitation of ranges of values herein are not intended to be limiting,referring instead individually to any and all values falling within therange, unless otherwise indicated herein, and each separate value withinsuch a range is incorporated into the specification as if it wereindividually recited herein. The words “about,” “approximately,”“substantially” or the like, when accompanying a numerical value, are tobe construed as including any deviation as would be appreciated by oneof ordinary skill in the art to operate satisfactorily for an intendedpurpose. Ranges of values and/or numeric values are provided herein asexamples only, and do not constitute a limitation on the scope of thedescribed embodiments. The use of any and all examples or exemplarylanguage (“e.g.,” “such as,” or the like) provided herein, is intendedmerely to better illuminate the embodiments and does not pose alimitation on the scope of the embodiments or the claims. No language inthe specification should be construed as indicating any unclaimedelement as essential to the practice of the disclosed embodiments.

In the following description, it is understood that terms such as“first,” “second,” “top,” “bottom,” “above,” “below,” “up,” “down,” andthe like, are words of convenience and are not to be construed aslimiting terms unless specifically stated.

Spiral forming devices, systems, and methods of the present disclosureare described with respect to forming segments of towers for supportingwind turbines. However, this is by way of example and should not beunderstood to limit the presently disclosed devices, systems, andmethods in any way. That is, in general, the spiral forming devices,systems, and methods of the present disclosure can be used to produce avariety of useful tubular structures such as, for example, towers,pilings, other structural pieces for civil engineers (e.g., columns),pipelines, spiral ducting, and the like.

Referring to FIG. 1, a wind turbine assembly 10 includes a wind turbine12 supported by a tower 14. The tower 14 can have a diameter thatdecreases along the length of the tower 14 so that the top, where thewind turbine 12 is attached, has a smaller diameter than the base, wherethe tower 14 is fixedly secured to the ground or other rigid surface.The axially tapering diameter of the tower 14 can be useful, forexample, for addressing competing considerations of efficient use ofmaterial while providing structural strength to support the loadsexerted by or on the wind turbine 12 in the field. That is, in general,loads vary along the axial direction of the tower 14, with larger loadstypically experienced toward the base of the tower 14 and lower loadstypically experienced toward the top of the tower 14. Thus, for a givenmaterial thickness, the axial taper of the tower 14 can result in theuse of less material as compared to a tower having only a singlediameter selected to withstand a maximum stress load at the base. Whilethe use of less material can be achieved by varying the diameter of thetower 14, it should be appreciated that less material can further, orinstead, be achieved through the use of varying material thickness in adirection extending away from the base of the tower 14. More generally,changes in diameter, material type, material thickness, and combinationsthereof can be varied along the tower 14 to achieve suitable designcharacteristics for withstanding loading while making efficient use ofmaterial.

The tower 14 can be fabricated from segments formed using a continuousspiral forming process in which, as described in greater detail below, aplanar form of a stock material can be rolled into shape and joinedalong one or more spiral seams to form a tubular structure, such as astructure having a frusto-conical shape. When fabricated in this manner,variations in structural characteristics of the tower 14 along the axisof the tower 14 from the base to the top—whether achieved throughchanges in diameter, material type, material thickness, or combinationsthereof—can require managing transitions in planar sheets forming theplanar form of the stock material. As described herein, thesetransitions can be managed by controlling shape and relative orientationof the plurality of planar sheets forming the stock material and/or bycontrolling a position of a roll bender used to curve the planar form ofthe stock material into a curved configuration. Such control of thesheets through these transitions can advantageously facilitate rollingthe sheets to a desired diameter with a reduced likelihood of dimples orother errors and, further or instead, can facilitate fit up betweenadjacent sheets in the curved configuration to increase the likelihoodof meeting manufacturing tolerances in the final structure.

Referring now to FIG. 2, the tower 14 may include a plurality of conicalsegments 16 joined (e.g., welded) to one another. For example, theconical segments 16 can be fabricated at a mill, according to themethods described herein, and then shipped to the field, where thefrusto-conical segments 16 can be welded or otherwise mechanicallycoupled to one another to form the tower 14. While this provides auseful, modular structure, the tower 14 may instead be formed of aunitary conical segment without departing from the scope of the presentdisclosure. The tower 14 can, further or instead, include one or morecylindrical segments and, thus, more generally can be understood toinclude any manner and form of tubular segments.

Each conical segment 16 can have either an actual peak or a virtualpeak. For example, one of the conical segments 16 can be shaped as acone and, therefore, have an actual peak at its apex. Additionally, oralternatively, one or more of the conical segments 16 can be shaped as atruncated structure, such as a frusto-conical structure, and, therefore,can have a “virtual peak” at the point at which the taper wouldeventually decrease to zero if the structure were not truncated. Unlessotherwise specified or made clear from the context, the devices,systems, and methods described herein should be understood to beapplicable to conical segments 16 having either an actual peak or avirtual peak. More generally, unless otherwise specified or made clearfrom the context, devices, systems and methods described herein shouldbe understood to be applicable to any of various different types oftubular structures.

Referring now to FIG. 3, each conical segment 16 can include a firstcurved sheet 18 a and a second curved sheet 18 b. In general, it shouldbe appreciated that each conical segment 16 can include a greater numberof curved sheets, as necessary, to meet various different designrequirements associated with the conical segment 16. Other curved sheetsforming each conical segment 16 can be coupled to one another in amanner analogous to the coupling of the first curved sheet 18 a and 18 band, thus, for the sake of efficient explanation, the coupling of thefirst curved sheet 18 a to the second curved sheet 18 b is describedherein as an illustrative example that shall be understood to beapplicable to the coupling of the other curved sheets in each conicalsegment 16, unless otherwise specified or made clear from the context.

The first curved sheet 18 a and the second curved sheet 18 b can bejoined end-to-end along a lateral seam 20, as described in greaterdetail below, prior to rolling the first curved sheet 18 a and thesecond curved sheet 18 b. The first curved sheet 18 a and the secondcurved sheet 18 b can be, for example, metal such that the first curvedsheet 18 a and the second curved sheet 18 b can be curved and joined toone another using any one or more of the various different devices,systems, and methods described herein. In instances in which the firstcurved sheet 18 a and the second curved sheet 18 b are metal, thelateral seam 20 can be a weld formed using any one or more of thevarious different devices, systems, and methods described herein.

The lateral seam 20 can orient the curved first sheet 18 a and thecurved second sheet 18 b relative to one another to facilitatealignment, or fit up, of longitudinal edges of the first curved sheet 18a, the second curved sheet 18 b, and one or more other adjacent curvedsheets to form a first spiral seam 22 a properly aligned with a secondspiral seam 22 b between the second curved sheet 18 b and another curvedsheet. That is, longitudinal edges of the first curved sheet 18 a andthe second curved sheet 18 b can be orientated relative to one anothersuch that the lateral seam 20, the first spiral seam 22 a, and thesecond spiral seam 22 b come together in a specific orientation at theintersection 24. More specifically, the lateral seam 20, the firstspiral seam 22 a, and the second spiral seam 22 b can come together atthe intersection 24 in a “T”-shape. As used herein, a “T” shape shall beunderstood to include any manner and form of intersection of threeseams. For example, the lateral seam 20, the first spiral seam 22 a, andthe second spiral seam 22 b can be oblique relative to one another atthe intersection 24. As compared to an “X”-shaped intersection formedthrough the intersection of four seams, the formation of theintersection 24 in the “T”-shape can reduce the likelihood of welddefects at the intersection, inaccuracy in alignment of seams, and/orinaccuracy of the rolled diameter and, thus, can facilitatemanufacturing tubular structures having improved dimensional tolerance.

The first spiral joint 22 a and the second spiral joint 22 b may extendin a spiral which, as used herein, includes a joint that wraps aroundthe circumference of a structure while also extending along the lengthof the structure. For example, the term spiral can be any curvilinearshape extending substantially around the circumference of a structurewhile also extending along the length of the structure. As used herein,a curvilinear shape should be understood to refer to a mathematicalfunction that is differentiable everywhere along the shape. Accordingly,the use of the term spiral, as used herein, should be understood toinclude one or more curves on a conical or cylindrical surface andshould further be understood to exclude sharp corners, such as the typeof corners formed by the intersection of straight segments.

The first spiral joint 22 a and the second spiral joint 22 b may eachextend circumferentially about a longitudinal axis defined by theconical segment 16. A radial distance from the first spiral joint 22 ato the longitudinal axis of the conical segment 16 is monotonicallyvarying in a direction along the longitudinal axis. Similarly, a radialdistance from the second spiral joint 22 b to the longitudinal axis ismonotonically varying in a direction along the longitudinal axis.Collectively, the curved first sheet 18 a, the curved second sheet 18 b,and the other curved sheets of the conical segment 16 form a structurethat narrows from one end to another. This can be, for example, a lineartaper that forms a substantially conical shape of the conical segment16.

Referring now to FIGS. 4 and 5, a collection 40 of a plurality of planarsheets can be collectively dimensioned to form, in a spiralconfiguration, a tubular structure. For example, the collection 40 ofthe plurality of planar sheets can be collectively dimensioned to form,in a curved configuration, a frusto-conical structure without in-planedeformation of the planar sheets such as the conical segment 16 (FIG.3). The plurality of planar sheets can include a first planar sheet 18a′ and a second planar sheet 18 b′. It should be appreciated that sheetsrepresented by the primed numbers in FIGS. 4A and 4B represent planarforms of respective curved sheets in FIG. 3. Accordingly, the firstplanar sheet 18 a′ should be understood to be a planar, or flat, form ofthe curved sheet 18 a before rolling, and the second planar sheet 18 b′should be understood to be a planar, or flat, form of the curved sheet18 b before rolling. As described in greater detail below, the firstplanar sheet 18 a′ and the second planar sheet 18 b′ can be positionedin an abutting relationship to one another and, so positioned, can becoupled together (e.g., welded) to form a stock material 50 in planarform that can be fed into any one or more of the curving devicesdescribed herein to form a tubular structure, such as the conicalsegment 16 (FIG. 3).

The first planar sheet 18 a′ can have a pair of first longitudinal edges42, a mating edge 44, and an alignment edge 46. In general, the matingedge 44 and the alignment edge 46 together define a nonlinear pathextending between the first longitudinal edges 42 (e.g., extending fromone of the first longitudinal edges 42 to another one of the firstlongitudinal edges 42). That is, neither the mating edge 44 nor thealignment edge 46 is collinear with either of the first longitudinaledges 42. The mating edge 44 can, for example, include a linear segmenthaving a lateral dimension, and the alignment edge 46 can include alinear segment having a lateral dimension intersecting the at least onelinear segment of the mating edge 44 such that the overall shape of apath defined by the mating edge 44 and the alignment edge 46 isnonlinear from one of the first longitudinal edges 42 to another one ofthe first longitudinal edges 42. Further, or instead, the mating edge 44and the alignment edge 46 together can span an entire width of the firstplanar sheet 18 a′, from one of the first longitudinal edges 42 to theother one of the first longitudinal edges 42.

The second planar sheet 18 b′ can have a pair of second longitudinaledges 43 and a lateral edge 45. The lateral edge 45 can extend betweenthe second longitudinal edges 43. For example, the lateral edge 45 canextend an entire width of the second planar sheet 18 b′, from one of thesecond longitudinal edges 43 to the other one of the second longitudinaledges 43. In certain implementations, the lateral edge 45 can define alinear path between the second longitudinal edges 43. More generally,forming the mating edge 44 of the first planar sheet 18 a′ and thelateral edge 45 of the second planar sheet 18 b′ as simple geometriescan facilitate aligning the first planar sheet 18 a′ and the secondplanar sheet 18 b′ to establish an abutting relationship in which themating edge 44 of the first planar sheet 18 a′ complements the lateraledge 45 of the second planar sheet 18 b′.

The first planar sheet 18 a′ and the second planar sheet 18 b′ can bedimensioned to be positionable relative to one another in an abuttingrelationship in which the mating edge 44 of the first planar sheet 18 a′complements the lateral edge 45 between the second longitudinal edges 43of the second planar sheet 18 b′ and the alignment edge 46 of the firstplanar sheet 18 a′ is collinear with one of the second longitudinaledges 43 of the second planar sheet 18 b′. The stock material 50 formedthrough coupling the first planar sheet 18 a′ and the second planarsheet 18 b′ together in this orientation has multiple features thatcooperate to align curved sheets (e.g., the first curved sheet 18 a andthe second curved sheet 18 b in the conical segment 16 in FIG. 3) in theformation of a tubular structure. For example, as compared to joiningsheets by aligning four seams at an intersection (e.g., in an“X”-shape), the first curved sheet 18 a and the second curved sheet 18 b(FIG. 3) formed from the first planar sheet 18 a′ and the second planarsheet 18 b′, respectively, can be joined to one another by aligningthree seams at an intersection (e.g., in a “T”-shape). Each seampotentially adds inaccuracies in alignment and geometry. Therefore,because a “T”-shaped intersection has one less seam than an “X”-shapedintersection, it should be understood that curved sheets can be moreaccurately aligned at a “T”-shaped intersection than at an “X”-shapedintersection.

As used herein, a complementing relationship between two edges should beunderstood to include a relationship in which the edges match oneanother along an entirety of each edge. For example, a complementingrelationship can exist between two straight edges, between twocurvilinear edges, between two edges with multiple segments, andcombinations thereof, provided that the two edges can be placed againstone another along an entirety of each edge. Thus, as a specific example,in the abutting relationship between the first planar sheet 18 a′ andthe second planar sheet 18 b′, the first planar sheet 18 a′ and thesecond planar sheet 18 b′ can form a continuous surface (e.g., to definea seam along which the first planar sheet 18 a′ and the second planarsheet 18 b′ can be joined to one another through conventional weldingtechniques).

In general, it should be understood that the orientation of the firstlongitudinal edges 42 of the first planar sheet 18 a′ to the secondlongitudinal edges 43 of the second planar sheet 18 b′ is such that, inthe three-dimensional form of a tubular structure (e.g., the conicalsegment 16 in FIG. 3), one of the first longitudinal edges 42 can beadjacent to one of the second longitudinal edges 43 to form at least aportion of a spiral seam along the tubular structure. In the abuttingrelationship between the first planar sheet 18 a′ and the second planarsheet 18 b′, one of the first longitudinal edges 42 of the first planarsheet 18 a′ can be oblique relative to one of the second longitudinaledges 43 of the second planar sheet 18 b′. That is, one of the firstlongitudinal edges 42 of the first planar sheet 18 a′ can be neitherparallel nor perpendicular to one of the second longitudinal edges 43.The degree of the oblique orientation can be a function of thedimensions of the tubular structure and, optionally, the portion of thetubular structure to be formed by the first planar sheet 18 a′ and thesecond planar sheet 18 b′.

In certain implementations, in the abutting relationship between thefirst planar sheet 18 a′ and the second planar sheet 18 b′, one of thefirst longitudinal edges 42 of the first planar sheet 18 a′ can contactone of the second longitudinal edges 43 of the second planar sheet 18 b′to define a substantially continuous edge (e.g., an edge that isuninterrupted except for a seam between the first planar sheet 18 a′ andthe second planar sheet 18 b′) extending from the first planar sheet 18a′ to the second planar sheet 18 b′. For example, one of the firstlongitudinal edges 42 of the first planar sheet 18 a′ can be in contactwith one of the second longitudinal edges 43 of the second planar sheet18 b′ along only a line of contact (e.g., along a line of contactdefined by a thickness dimension of one or both of the first planarsheet 18 a′ and the second planar sheet 18 b′). Further or instead, theother one of the first longitudinal edges 42 and the other one of thesecond longitudinal edges 43 can be spaced apart from one another by thealignment edge 46.

In general, the first planar sheet 18 a′ and the second planar sheet 18b′ can be, for example, formed of metal, such as steel or any othermaterial suitable for spiral forming. The first planar sheet 18 a′ andthe second planar sheet 18 b′ can have any of various differentthicknesses suitable for achieving desired structural performance of theconical segment (FIG. 3) into which the first planar sheet 18 a′ and thesecond planar sheet 18 b′ will be incorporated. For example, the firstplanar sheet 18 a′ and the second planar sheet 18 b′ can have athickness of greater than about 10 mm and less than about 50 mm forutility scale wind tower applications. Additionally, or alternatively,the first planar sheet 18 a′ can have, for example, a first thickness,and the second planar sheet 18 b′ can have a second thickness equal tothe first thickness. The use of the same material having the samethickness can facilitate, for example, controlling curvature transitionsbetween the first planar sheet 18 a′ and the second planar sheet 18 b′.In certain implementations, the first planar sheet 18 a′ and the secondplanar sheet 18 b′ can have different thicknesses and, as described ingreater detail below, such transitions in thickness can be managed toachieve appropriate curvature. As used herein, the respectivethicknesses of the first planar sheet 18 a′ and the second planar sheet18 b′ shall be understood to refer to a dimension of the respectivesheet in a direction perpendicular to a plane defined by each respectivesheet.

In general, the first planar sheet 18 a′ and the second planar sheet 18b′ can each have an elongate shape. That is, each of the first planarsheet 18 a′ and the second planar sheet 18 b′ can each have a shape thatis substantially longer than a maximum width defined by the respectivefirst longitudinal edges 42 and the second longitudinal edges 43. Theelongate shape can facilitate, for example, curving a respective sheetwithout requiring excessive forces to be provided by the curving device.Further, or instead, the elongate shape can be useful for forming thefirst planar sheet 18 a′ and the second planar sheet 18 b′ from material(e.g., steel) that is ubiquitously available in standard sizes. That is,the length of the material in the longitudinal direction can be selectedbased on a diameter of the structure being formed while the width of thematerial can be a standard, commercially available size.

In certain implementations, such as in the formation of a conicalstructure, the first planar sheet 18 a′ and the second planar sheet 18b′ can have different lengths. For example, as a diameter of a conicalstructure decreases in an axial direction defined by the conicalstructure, shorter lengths of planar sheets can be used to form theconical structure. That is, as the diameter of a conical structuredecreases in the axial direction defined by the conical structure, lessmaterial can be used in the conical structure. The use of less materialcan have significant advantages with respect to cost savings and,further or instead, can facilitate achieving an allowed stress responsealong the conical structure.

The pair of first longitudinal edges 42 of the first planar sheet 18 a′can be parallel to one another to define a first width along the firstplanar sheet 18 a′. Similarly, the pair of second longitudinal edges 43can be parallel to one another to define a second width along the secondplanar sheet 18 b′. In certain implementations, the first width definedby the first longitudinal edges 42 can be equal to the second widthdefined by the second longitudinal edges 43. Such equal width dimensionscan, for example, control dimensions of the planar form of the stockmaterial 50. Additionally, or alternatively, such equal width dimensionscan facilitate accurately controlling a spiral seam (e.g., the firstspiral seam 22 a) formed along a curved configuration of the stockmaterial 50. In certain instances, equal widths of the first planarsheet 18 a′ and the second planar sheet 18 b′ can have certaincommercial advantages, such as facilitating forming structures fromcommercially available, standard-sized sheets. That is, as compared tocutting sheets to custom widths and producing scrap in the process, thefirst planar sheet 18 a′ and the second planar sheet 18 b′ can be formedof the same width from standard material purchased in standard bulk form(e.g., on a coil) and results in less scrap.

Referring now to FIGS. 3-5, the planar form of the stock material 50 canbe curved using, for example, any of the devices, systems, and methodsdescribed herein such that the first planar sheet 18 a′ is formed intothe first curved sheet 18 a and, similarly, the second planar sheet 18b′ is formed into the second curved sheet 18 b. In general, unlessotherwise specified or made clear from the context, it should beunderstood that the first curved sheet 18 a has the same edges as thefirst planar sheet 18 a′, and the second curved sheet 18 b has the sameedges as the second planar sheet 18 b′. By curving the edges of thefirst planar sheet 18 a′ and the second planar sheet 18 b′, the firstcurved sheet 18 a and the second curved sheet 18 b can be aligned withone another such that the alignment edge 46 of the first curved sheetforms at least a portion of the first spiral seam 22 a with one of thesecond longitudinal edges 43 of the second curved sheet 18 b. Further,or instead, the first curved sheet 18 a and the second curved sheet 18 bcan be aligned with one another such that one of the first longitudinaledges 42 of the first curved sheet 18 a and one of the secondlongitudinal edges 43 of the second curved sheet 18 b are joined alongthe first spiral seam 22 a.

Referring now to FIGS. 6 and 7, a fabrication system 60 can include astock source 61, a feed system 62, a curving device 63, a joining system64, and a control system 65. As described in greater detail below, thefabrication system 60 can be operable to fabricate the conical segments16 (FIG. 3) according to any one or more of the spiral forming methodsdisclosed herein. The control system 65 may control at least one of thestock source 61, the feed system 62, the curving device 63, and thejoining system 64. In some implementations, the control system 65 cancontrol more or fewer components of the fabrication system 60, and anycombinations thereof. For example, the control system 65 canadditionally control a runout system to move formed portions of theconical segment 16 in a direction away from the curving device 63 and/orthe joining system 64. For clarity of explanation, the operation of thefabrication system 60 and the methods of spiral forming disclosed hereinare described with respect to the conical segments 16 described above.It should be appreciated, however, that other types of tubularstructures (e.g., substantially cylindrical structures) may also orinstead be fabricated using these techniques.

The control system 65 can include a processing unit 66 and a storagemedium 67 in communication with the processing unit 66. The processingunit 66 can include one or more processors, and the storage medium 67can be a non-transitory, computer-readable storage medium. The storagemedium 67 can store computer-executable instructions that, when executedby the processing unit 66, cause the fabrication system 60 to performone or more of the spiral forming methods described herein. Optionally,the control system 65 can include an input device (e.g., a keyboard, amouse, and/or a graphical user interface) in communication with theprocessing unit 66 and the storage medium 67 such that the processingunit 66 is additionally, or alternatively, responsive to input receivedthrough the input device as the processing unit 66 executes one or moreof the spiral forming methods described herein.

More generally, the control system 65 may include any processingcircuitry configured to receive sensor signals and responsively controloperation of the fabrication system 60. This can, for example, includededicated circuitry configured to execute processing logic as desired orrequired, or this can include a microcontroller, aproportional-integral-derivative controller, or any other programmableprocess controller. This can also or instead include a general purposemicroprocessor, memory, and related processing circuitry configured bycomputer executable code to perform the various control steps andoperations described herein.

The stock source 61 can include a plurality of planar sheets of sourcematerial, which can be stored in a magazine or other suitable dispenserto facilitate selection and loading of the plurality of sheets duringmanufacturing. For the sake of efficient and clear explanation, theplurality of planar sheets is described as including the first planarsheet 18 a′ and the second planar sheet 18 b′ and the fabrication system60 is described with respect to the first planar sheet 18 a′ and thesecond planar sheet 18 b′. It should be appreciated, however, that theplurality of planar sheets can include any number of additional sheetsas required for the formation of the conical segment 16.

Between the stock source 61 and the feed system 62, the first planarsheet 18 a′ and the second planar sheet 18 b′ can be joined (e.g.,welded) to one another at the lateral seam 20 to form the planar form ofthe stock material 50. In general, the lateral seam 20 can be oblique toa feed direction “F” at which the planar form of the stock material 50enters the curving device 63.

The feed system 62 may be operable to transport the planar form of thestock material 50 from the stock source 61 to and/or through the curvingdevice 63. The feed system 62 can include, for example, one or morepairs of drive rolls 72. In use, the drive rolls 72 can pinch the planarform of the stock material 50 such that rotation of the drive rolls 72can move the planar form of the stock material 50 along the feeddirection “F.” In certain implementations, the feed direction “F” can besubstantially constant (e.g., with the one or more pairs of drive rolls72 in a substantially stationary position as the rotation of the one ormore pairs of drive rolls 72 moves the planar form of the stock material50 to and/or through the curving device 63). Additionally, oralternatively, the feed direction “F” can change such that the planarform of the stock material 50 undergoes rotational motion and/orsubstantially rotational motion as the planar form for the stockmaterial 50 is moved to and through the curving device 63. Such changesin the feed direction “F” can be useful for aligning edges of the stockmaterial 50 to form any one or more of the structures described herein.Examples of such changes in the feed direction “F” to produce rotationaland/or substantially rotational motion as part of the fabricationprocess of tubular structures are described in U.S. Pat. No. 9,302,303,issued Apr. 5, 2016, and U.S. Pat. App. Pub. No. 2015/0273550, filedMar. 28, 2014, the entire contents of each of which are incorporatedherein by reference. More generally, any equipment suitable for movingplanar material according to any of various different techniques knownin the art can be used to move the planar form of the stock material 50from the stock source 61 to, and in some instances through, the curvingdevice 63. Such equipment can include, for example, robotic arms,pistons, servo motors, screws, actuators, rollers, drivers,electromagnets, or combinations thereof.

The curving device 63 can impart a controllable degree of curvature tothe planar form of the stock material 50 fed into it, preferably withoutimparting in-plane deformation to the stock material 50. The curvingdevice 63 can, for example, include a roll bender 72 including rollbanks 75 a, 75 b, 75 c positioned relative to one another and to theplanar form of the stock material 50 to impart curvature to the planarform of the stock material 50 fed through the roll banks 75 a, 75 b, 75c. In certain instances, the roll banks 75 a, 75 b, 75 c can be arrangedas a triple-roll and, further or instead, the roll banks 75 a, 75 b, 75c can be movable relative to one another to vary a bending momentapplied to the stock material 50 moving through the roll bender 72. Eachroll bank 75 a, 75 b, 75 cc can include, for example, a plurality ofindividual rollers independently rotatable relative to one another andarranged along a respective axis defined by the respective roll bank 75a, 75 b, 75 c. Further, or instead, the individual rollers of therespective roll banks 75 a, 75 b, 75 c can be positionable relative to arespective axis defined by the respective roll bank 75 a, 75 b, 75 c(e.g., through an actuation signal received by the control system 65).

In general, the curving device 63 can impart a bending moment to theplanar form of the stock material 50 to form the first planar sheet 18a′ and the second planar sheet 18 b′ into the first curved sheet 18 aand the second curved sheet 18 b, respectively. The first planar sheet18 a′ and the second planar sheet 18 b′ can be orientated relative toone another such that, through the application of bending moments toform the first curved sheet 18 a and the second curved sheet 18 b, thealignment edge 46 of the first curved sheet 18 a and one of the secondlongitudinal edges 43 of the second curved sheet 18 b can be adjacent toone of the first longitudinal edges 42 of the first curved sheet 18 a.More specifically, these edges can be adjacent to one another along aspiral path.

The joining system 64 can mechanically couple the alignment edge 46 ofthe first curved sheet 18 a and one of the second longitudinal edges 43of the second curved sheet 18 b to one of the first longitudinal edges42 of the first curved sheet 18 a to form at least a portion of thefirst spiral seam 22 a. Similarly, the joining system 64 canmechanically couple edges forming the second spiral seam 22 b. Thejoining system 64 can include, for example, a welder that welds thealignment edge 46 of the first curved sheet 18 a and one of the secondlongitudinal edges 42 of the second curved sheet 18 b to one of thefirst longitudinal edges 42 of the first curved sheet 18 a using anysuitable welding technique. A variety of techniques for welding areknown in the art and may be adapted for joining one or more edgestogether as contemplated herein. This can, for example, include anywelding technique that melts a base metal or other material along thefirst spiral seam 22 a, the second spiral seam 22 b, or both, optionallyalong with a filler material that is added to the joint to improve thestrength of the bond. Conventional welding techniques suitable forstructurally joining metal include, by way of example and notlimitation: gas metal arc welding (GMAW), including metal inert gas(MIG) and/or metal active gas (MAG); submerged arc welding (SAW); laserwelding; and gas tungsten arc welding (also known as tungsten, inert gasor “TIG” welding); and many others. These and any other techniquessuitable for forming a structural bond between the first curved sheet 18a and the second curved sheet 18 b can be adapted for use in the joiningsystem 64 as contemplated herein. The mechanical coupling imparted bythe joining system 64 can be, for example, continuous along the firstspiral seam 22 a, the second spiral seam 22 b, or both to provideenhanced structural strength of the conical segment 16. The mechanicalcoupling may also or instead include intermittent coupling (e.g., atfixed distances) along the first spiral seam 22 a, the second spiralseam 22 b, or both to facilitate, for example, faster throughput forapplications in which structural strength of the conical segment 16 isnot a key design consideration.

Referring now to FIG. 8, a flowchart of an exemplary method 80 of spiralforming a structure is shown. It should be appreciated that theexemplary method 80 can be carried out, for example, by any one or moreof the fabrication systems described herein to form any of the tubularstructures described herein, including but not limited to a cylinder ora cone (e.g., a frusto-conical structure or segment). For example, oneor more steps in the exemplary method 80 can be carried out by aprocessing unit of a control system (e.g., the processing unit 66 of thecontrol system 65 in FIG. 6). Additionally, or alternatively, one ormore steps in the exemplary method 80 can be carried out by an operatorproviding inputs (e.g., through a keyboard, a mouse, and/or a graphicaluser interface) to a control system such as the control system 65 ofFIG. 6.

As shown in step 81, the exemplary method 80 can include obtaining aplurality of planar sheets. For example, the plurality of planar sheetscan be obtained from a stock source, such as the stock source 61 in FIG.6. In general, the plurality of planar sheets can include any number andform of planar sheets collectively dimensioned for forming a tubularstructure, such as a cylinder or a cone (e.g., the frusto-conicalsegment 16 in FIG. 3). More specifically, the plurality of planar sheetscan include a first planar sheet and a second planar sheet such as, forexample, the first planar sheet 18 a′ and the second planar sheet 18 b′in FIG. 4. Thus, the first planar sheet can have a pair of firstlongitudinal edges, a mating edge, and an alignment edge as describedabove with respect to the first planar sheet 18 a. Similarly, the secondplanar sheet can have a lateral edge and a pair of second longitudinaledges, such as described above with respect to the second planar sheet18 b′. Further, or instead, the first planar sheet and the second planarsheet can each have an elongate shape and, in instances in which thesesheets are to be formed into a conical segment such as the conicalsegment 16 in FIG. 3, the first planar sheet and the second planar sheetcan have different lengths (e.g., the first planar sheet can be longerthan the second planar sheet).

As shown in step 82, the exemplary method 80 can include positioning thefirst planar sheet and the second planar sheet relative to one anotherin an abutting relationship. For example, in the abutting relationship,the mating edge of the first planar sheet can complement the lateraledge of the second planar sheet between the second longitudinal edges.Further, with the mating edge of the first planar sheet complementingthe lateral edge of the second planar sheet, the alignment edge of thefirst planar sheet can be collinear with one of the second longitudinaledges of the second planar sheet.

As shown in step 83, the exemplary method 80 can include coupling (e.g.,welding) the mating edge of the first planar sheet to the lateral edgeof the second planar sheet along a lateral seam to form a stock materialin planar form. It should be appreciated that the shape of the lateralseam can follow the shape of the abutting relationship between the firstplanar sheet and the second planar sheet. Thus, more generally, thelateral seam can include at least one linear segment, at least onenon-linear segment, or both.

As shown in step 84, the exemplary method 80 can include curving thestock material into a curved configuration. For example, as a planarform of the stock material is moved through a curving device, such asthe curving device 63 in FIGS. 6 and 7, bending moments can be appliedto the stock material to form a curved configuration of the stockmaterial (e.g., without imparting in-plane deformation to the stockmaterial).

As shown in step 85, the exemplary method can include spiral welding thestock material to form a tubular structure, such as a frusto-conicalstructure. As an example, spiral welding can include coupling one of thelongitudinal edges of the first curved sheet (e.g., the first planarsheet in a curved configuration imparted through a curving step, such asstep 84) to one of the second longitudinal edges of the second curvedsheet (e.g., the second planar sheet in a curved configuration impartedthrough a curving step, such as step 84).

While certain embodiments have been described, other embodiments areadditionally or alternatively possible.

For example, while joining a first edge region to a second edge regionhas been described as including welding, other methods of joining edgeregions to one another are additionally or alternatively possible.Examples of such other methods include adhesive bonding, spot welding,seam locking, and/or mechanical fastening with bolts, rivets and thelike, as well as combinations of the foregoing.

As another example, while planar sheets have been described as havingcertain edge shapes, other edge shapes are additionally or alternativelypossible. For example, as referring now to FIG. 9, a collection 90 ofplanar sheets can include a first planar sheet 92 a and a second planarsheet 92 b. In general, unless otherwise specified or made clear fromthe context, the collection 90 of planar sheets can be formed into atubular structure using any one or more of the devices, systems, andmethods described herein.

The first planar sheet 92 a can include a mating edge 94 and analignment edge 96. The mating edge 94 can include, for example, aplurality of linear segments 97 a, 97 b. The plurality of linearsegments 97 a, 97 b can be angled relative to one another. The secondplanar sheet 92 b can include a lateral edge 98 shaped to complement theshape defined by the linear segments 97 a, 97 b of the first planarsheet 92 a. Thus, for example, the lateral edge 98 can define anonlinear path such that the lateral edge 98 complements the linearsegments 97 a, 97 b of the first planar sheet 92 a. The nonlinear pathof the lateral edge 98 can be, for example, define a chevron or anothershape defined by linear or straight segments angled relative to oneanother.

As another example, while the planar sheets have been described ashaving edges with one or more linear segments to facilitate alignment ina given orientation suitable for formation of tubular structures, otheredge shapes are additionally or alternatively possible. For example, oneor more edges of the planar sheets can include a curvilinear shape. As aspecific example, a transition between the linear segments 97 a, 97 b ofthe first planar sheet 92 a can be rounded. Additionally, oralternatively, the lateral edge 98 of the second planar sheet 92 b caninclude a corresponding shape including a rounded segment matching therounded transition between the linear segments 97 a, 97 b. Moregenerally, curvilinear shapes of one or more portions of edges describedherein should be understood to be substitutable for linear shapes,unless otherwise specified or made clear from the context, provided thatother sheets include corresponding edges to match such curvilinearshapes.

As still another example, while the planar sheets have been described ashaving equal thickness, other arrangements of thickness are additionallyor alternatively possible. For example, sequential sheets in a pluralityof planar sheets can have different thicknesses, material properties, orboth. Such differences in thickness and/or material properties areuseful, for example, for achieving desired variations in structuralperformance along an axis of a tubular structure and, in certaininstances, can facilitate achieving structural performance targets usingless material and/or less expensive material.

While differences in one or more of thickness and material properties ofsequential sheets can be useful for achieving efficient use of material,such differences can be associated with differences in respectivecurvature responses of the sheets to a given bending moment applied by acurving device. Thus, in general, the application of a single bendingmoment (e.g., through a fixed orientation of a curving device) through atransition between sheets having different thickness and/or materialproperties can lead to incorrect rolling during such a transition. Forexample, application of a bending moment suitable to curve a thickersheet can result in over-rolling an adjacent thinner sheet such that thethinner sheet will have a higher curvature than desired. As anotherexample, application of a bending moment suitable to curve a thinnersheet can result in under-rolling an adjacent thicker sheet such thatthe thicker sheet will have a lower curvature than desired. Each ofthese errors in rolling can result in misalignment in sections of atubular structure being formed and rolled sections having curvatureother than desired, which can create challenges for forming the tubularstructure according to a given manufacturing tolerance.

As yet another example, while lateral portions of sequential sheets havebeen described in the context of being joined to one another to form aportion of a tubular structure, it should be appreciated that theopposite lateral portion of each sheet can have the same or a differentshape, as required for mating with another sheet in the sequence. Thus,for example, a given sheet can include respective alignment edges andmating edges along each lateral portion of the sheet. Further orinstead, a given sheet can include respective lateral edges along eachlateral portion of the sheet.

Referring now to FIG. 7 and FIG. 10, the stock material 50 including thefirst planar sheet 18 a′ and the second planar sheet 18 b′ can be movedin the feed direction F. For the sake of clarity of illustration of thelateral seam 22 a moving through the roll bender 74, only the roll bank75 a of the roll bender 74 is shown in FIG. 10. The lateral seam 20corresponding to the abutting relationship of the first planar sheet 18a′ and the second planar sheet 18 b′ can have a length in the feeddirection “F,” and this length of the abutting relationship of the firstplanar sheet 18 a′ and the second planar sheet 18 b′ in the feeddirection “F” can define a transition length 100. Because the feeddirection “F” is oblique relative to the lateral seam 20, it should beappreciated that the transition length 100 is finite. More specifically,the first planar sheet 18 a′ and the second planar sheet 18 b′ can bedimensioned relative to one another such that the lateral seam 20 and,thus, the transition length 100 can have a length sufficient toaccommodate application of multiple different bending moments as thestock material 50 moves through the roll bender 74 in the feed direction“F.” In certain implementations, the feed direction “F” can be changedas the stock material 50 is moved to and/or through the curving device63 and, in particular, the stock material 50 can undergo rotationaland/or substantially rotational motion as the stock material moves toand/or through the curving device 63.

In general, the bending moment applied by the roll bender 74 to thefirst planar sheet 18 a′ and the second planar sheet 18 b′ along thetransition length 100 can be changed to account for differences incurvature response of the first planar sheet 18 a′ and the second planarsheet 18 b′. For example, as the transition length 100 moves through theroll bender 74, the relative spacing of the roll banks 74 a, 74 b, and74 c can be adjusted to change a bending moment applied to the material.More specifically, a set position of the roll banks 74 a, 74 b, and 74 ccan be controlled, as described in greater detail below, to account fordifferences in curvature response (e.g., as a result of differences inthickness, material properties, or both) of the first planar sheet 18 a′and the second planar sheet 18 b′.

Referring now to FIG. 11, a flowchart of an exemplary method 110 ofsheet transitioning in a spiral forming process is shown. It should beappreciated that the exemplary method 110 can be carried out, forexample, by any one or more of the fabrication systems described hereinto reduce the likelihood of over-rolling or under-rolling abuttingplanar sheets corresponding to a transition in thickness and/or materialproperties of a tubular structure, such as a cylinder or a cone (e.g., afrusto-conical structure or segment). For example, one or more steps inthe exemplary method 110 can be carried out by a processing unit of acontrol system (e.g., the processing unit 66 of the control system 65 inFIG. 6). Additionally, or alternatively, one or more steps in theexemplary method 110 can be carried out by an operator providing inputs(e.g., through a keyboard, a mouse, and/or a graphical user interface)to a control system such as the control system 65 of FIG. 6).

As shown in step 112, the exemplary method 110 can include moving afirst planar sheet and a second planar sheet in a feed direction throughroll banks of a roll bender (e.g., the roll banks 75 a, 75 b, 75 c ofthe roll bender 74 in FIG. 7). The feed direction can be, for example,oblique relative to an axis defined by one or more of the roll banks ofthe roll bender. The first planar sheet and the second planar sheet canbe any one or more of the various different planar sheets describedherein. Thus, for example, the first planar sheet and the second planarsheet can have the same maximum width in a direction perpendicularrespective longitudinal edges of the first planar sheet and the secondplanar sheet. The uniform width of the first planar sheet and the secondplanar sheet can have certain advantages, such as facilitating uniformand accurate fabrication of the first planar sheet and the second planarsheet and reducing scrap material.

The first planar sheet and the second planar sheet can be coupled (e.g.,welded) to one another in an abutting relationship, such as any of thevarious different abutting relationships described herein with respectto the lateral seam 20 (FIGS. 3, 5, and 10). The length of the abuttingrelationship between the first planar sheet and the second planar sheetalong the feed direction defines a transition length. In instances inwhich the first planar sheet and the second planar sheet have differentthicknesses and/or material properties, the transition length canrepresent a region in which the first planar sheet and the second planarsheet can have disparate responses to a given applied bending moment.Accordingly, as described in greater detail below, the bending momentapplied to the first planar sheet and the second planar sheet can beadjusted along the transition length to reduce the likelihood ofover-rolling and/or under-rolling the first planar sheet and the secondplanar sheet. It should be appreciated, therefore, that the size of thetransition length is an important factor in the application of multipledifferent bending moments to the first planar sheet and the secondplanar sheet along the transition length.

In certain implementations, the abutting relationship between the firstplanar sheet and the second planar sheet can include abutment along oneor more edges that are oblique to the feed direction and, further orinstead oblique relative to an axis defined by one or more roll banks ofthe roll bender, as the first planar sheet and the second planar sheetmove through the roll bender along the transition length. As a moregeneral principle, the abutting relationship between the first planarsheet and the second planar sheet can be oriented relative to the one ormore roll banks of the roll bender to achieve a suitable transitionlength and geometry.

As shown in step 114, the exemplary method 110 can include, within thetransition length, curving the first planar sheet and the second planarsheet with the roll banks of the roll bender set at a first position. Asused herein, “within the transition length” should be understood torefer to an action applied to the first planar sheet and the secondplanar sheet along the transition length. Thus, in the context ofcurving the first planar sheet and the second planar sheet, the term“within the transition length” should be understood to refer to theapplication of one or more bending moments to the first planar sheet andthe second planar sheet as the transition length moves in a feeddirection through the roll bender.

The first planar sheet can have a thickness different from a thicknessof the second planar sheet. That is, the thickness of the first planarsheet can be greater than or less than the thickness of the secondplanar sheet. Additionally, or alternatively, the first planar sheet andthe second planar sheet can be formed of different materials and, inparticular, can be formed of materials having different yield strength.More generally, the first planar sheet and the second planar sheet canhave different curvature responses to the roll banks of the roll benderset at the first position. That is, the bending moments exerted on thefirst planar sheet and the second planar sheet by the roll banks of theroll bender set at the first position can produce different amounts ofcurvature of the sheets along the portion of the transition length alongwhich the roll banks of the roll bender are set at the first position.

As shown in step 116, the exemplary method 110 can include, within thetransition length, curving the first planar sheet and the second planarsheet with the roll banks of the roll bender set at a second position.The second position of the roll banks of the roll bender can bedifferent than the first position of the roll banks of the roll bendersuch that changing from the first set position to the second setposition changes the bending moment applied to the first planar sheetand the second planar sheet along the transition length. Because ofdifferences in thickness and/or material properties, the first planarsheet and the second planar sheet can have different curvature responsesto the roll banks of the roll bender at the second position.Accordingly, the roll banks of the roll bender set at the secondposition can produce different amounts of curvature in the two sheetsalong the portion of the transition length along which the roll banks ofthe roll bender are set at the second position.

In general, it should be appreciated that the first set position of theroll banks of the roll bender and the second set position of the rollbanks of the roll bender can be selected to apply a desired bendingmoment profile to the first planar sheet and the second planar sheetalong the transition length. The desired bending moment profile can, forexample, reduce the amount of under-rolling and/or over-rollingexperienced by the first planar sheet and the second planar sheet alongthe transition length. As an example, in instances in which the firstplanar sheet is thicker than the second planar sheet, the first planarsheet and the second planar sheet can be curved by the roll banks of theroll bender set to the second position when more than half of thetransition length has moved past a center roll of the roll bender (e.g.,the roll bank 75 a of the roll bender 74). An analogous example existsin instances in which the second planar sheet is thicker than the firstplanar sheet—that is, in such instances, the first planar sheet and thesecond planar sheet can be curved by the roll banks of the roll benderset to the second position when less than half of the transition lengthhas moved past a center roll of the roll bender (e.g., the roll bank 75a of the roll bender 74). Thus, more generally, a transition from thefirst position to the second position can be based on the relativethickness of the first planar sheet to the second planar sheet, with,for example, the set position of a given sheet (e.g., the first planarsheet or the second planar sheet) being applied over more than half ofthe transition length in instances in which the given sheet is thickerthan the other sheet (e.g., the other one of the first planar sheet andthe second planar sheet) forming the transition length. Additionally, oralternatively, curving the first planar sheet and the second planarsheet with the roll banks of the roll bender set at the second positioncan include moving one or more of the roll banks of the roll benderrelative to one another from the first set position to the second setposition (e.g., as the transition length moves through the roll banks ofthe roll bender).

As shown in step 118, the exemplary method 110 can optionally include,along a length in the rolling direction within the transition length,curving the second planar sheet with the roll banks of the roll benderset at a third set position different from the second set position. Forexample, a respective curvature response of the second planar sheet tothe roll banks of the roll bender set to the third position can besubstantially equal to a respective curvature response of the firstplanar sheet to the roll banks of the roll bender set to the firstposition such that at least a portion of the first planar sheet and thesecond planar sheet are rolled at substantially the same diameter.

The above systems, devices, methods, processes, and the like may berealized in hardware, software, or any combination of these suitable forthe control, data acquisition, and data processing described herein.This includes realization in one or more microprocessors,microcontrollers, embedded microcontrollers, programmable digital signalprocessors or other programmable devices or processing circuitry, alongwith internal and/or external memory. This may also, or instead, includeone or more application specific integrated circuits, programmable gatearrays, programmable array logic components, or any other device ordevices that may be configured to process electronic signals. It willfurther be appreciated that a realization of the processes or devicesdescribed above may include computer-executable code created using astructured programming language such as C, an object orientedprogramming language such as C++, or any other high-level or low-levelprogramming language (including assembly languages, hardware descriptionlanguages, and database programming languages and technologies) that maybe stored, compiled or interpreted to run on one of the above devices,as well as heterogeneous combinations of processors, processorarchitectures, or combinations of different hardware and software. Atthe same time, processing may be distributed across devices such as thevarious systems described above, or all of the functionality may beintegrated into a dedicated, standalone device. All such permutationsand combinations are intended to fall within the scope of the presentdisclosure.

Embodiments disclosed herein may include computer program productscomprising computer-executable code or computer-usable code that, whenexecuting on one or more computing devices, performs any and/or all ofthe steps of the control systems described above. The code may be storedin a non-transitory fashion in a computer memory, which may be a memoryfrom which the program executes (such as random access memory associatedwith a processor), or a storage device such as a disk drive, flashmemory or any other optical, electromagnetic, magnetic, infrared orother device or combination of devices. In another aspect, any of thecontrol systems described above may be embodied in any suitabletransmission or propagation medium carrying computer-executable codeand/or any inputs or outputs from same.

The method steps of the implementations described herein are intended toinclude any suitable method of causing such method steps to beperformed, consistent with the patentability of the following claims,unless a different meaning is expressly provided or otherwise clear fromthe context. So, for example, performing the step of X includes anysuitable method for causing another party such as a remote user, aremote processing resource (e.g., a server or cloud computer) or amachine to perform the step of X. Similarly, performing steps X, Y and Zmay include any method of directing or controlling any combination ofsuch other individuals or resources to perform steps X, Y and Z toobtain the benefit of such steps. Thus, method steps of theimplementations described herein are intended to include any suitablemethod of causing one or more other parties or entities to perform thesteps, consistent with the patentability of the following claims, unlessa different meaning is expressly provided or otherwise clear from thecontext. Such parties or entities need not be under the direction orcontrol of any other party or entity, and need not be located within aparticular jurisdiction.

It will be appreciated that the methods and systems described above areset forth by way of example and not of limitation. Numerous variations,additions, omissions, and other modifications will be apparent to one ofordinary skill in the art. In addition, the order or presentation ofmethod steps in the description and drawings above is not intended torequire this order of performing the recited steps unless a particularorder is expressly required or otherwise clear from the context. Thus,while particular embodiments have been shown and described, it will beapparent to those skilled in the art that various changes andmodifications in form and details may be made therein without departingfrom the spirit and scope of this disclosure and are intended to form apart of the invention as defined by the following claims, which are tobe interpreted in the broadest sense allowable by law.

What is claimed is:
 1. A structure comprising: a first curved sheethaving a pair of first longitudinal edges parallel to one another; and asecond curved sheet having a pair of second longitudinal edges parallelto one another, the first curved sheet and the second curved sheetjoined to one another at a T-shape intersection of seams including afirst spiral seam defined by the first curved sheet and the secondcurved sheet, and the first curved sheet and the second curved sheetforming at least a portion of a tapered conical segment along the firstspiral seam, wherein one of the first longitudinal edges of the firstcurved sheet is joined to one of the second longitudinal edges of thesecond curved sheet along the first spiral seam, another one of thesecond longitudinal edges of the second curved sheet forms a portion ofa second spiral seam oblique to the first spiral seam at the T-shapeintersection of seams.
 2. The structure of claim 1, wherein the pair offirst longitudinal edges define a first width of the first curved sheet,the pair of second longitudinal edges define a second width of thesecond curved sheet, and the first width is equal to the second width.3. The structure of claim 1, wherein the pair of second longitudinaledges of the second curved sheet abut one another at the T-shapeintersection of seams.
 4. The structure of claim 1, wherein the firstcurved sheet and the second curved sheet are joined end-to-end along alateral seam extending between the pair of second longitudinal edges,and the T-shape intersection of seams includes the lateral seam.
 5. Thestructure of claim 1, wherein the first spiral seam wraps around acircumference of the tapered conical segment.
 6. The structure of claim1, wherein the first curved sheet has a first thickness, and the secondcurved sheet has a second thickness different from the first thickness.7. The structure of claim 1, wherein at least one seam of the T-shapeintersection of seams includes a weld.
 8. The structure of claim 7,wherein the first spiral seam includes the weld.
 9. A structurecomprising: a first curved sheet having a first thickness; and a secondcurved sheet having a second thickness different from the firstthickness of the first curved sheet, the first curved sheet and thesecond curved sheet joined to one another at a T-shape intersection ofseams including a first spiral seam defined by the first curved sheetand the second curved sheet, the first curved sheet and the secondcurved sheet forming at least a portion of a tapered conical segmentalong the first spiral seam, wherein the first curved sheet has a pairof first longitudinal edges, the second curved sheet has a pair ofsecond longitudinal edges, and one of the first longitudinal edges ofthe first curved sheet is joined to one of the second longitudinal edgesof the second curved sheet along the first spiral seam, another one ofthe second longitudinal edges of the second curved sheet forms a portionof a second spiral seam oblique to the first spiral seam at the T-shapeintersection of seams.
 10. The structure of claim 9, wherein the firstcurved sheet and the second curved sheet are joined end-to-end along alateral seam extending between the pair of second longitudinal edges,and the T-shape intersection of seams includes the lateral seam.
 11. Thestructure of claim 9, wherein the pair of second longitudinal edges ofthe second curved sheet abut one another at the T-shape intersection ofseams.
 12. The structure of claim 9, wherein the first spiral seam wrapsaround a circumference of the tapered conical segment.
 13. The structureof claim 9, wherein at least one seam of the T-shape intersection ofseams includes a weld.
 14. The structure of claim 13, wherein the firstspiral seam includes the weld.
 15. A structure comprising: a firstcurved sheet having a pair of first longitudinal edges parallel to oneanother; and a second curved sheet having a pair of second longitudinaledges parallel to one another, the first curved sheet and the secondcurved sheet joined together at a T-shape intersection of seams obliqueto one another, the T-shape intersection of seams including a firstspiral seam defined by the first curved sheet and the second curvedsheet, and the first curved sheet and the second curved sheet forming atleast a portion of a tapered conical segment along the first spiralseam.